For centuries, the medieval fishermen who sailed in the placid waters of Lake Nemi, 19 miles south of Rome, knew a secret. It was said that the rotting timbers of a gigantic ancient shipwreck lurked below the water’s quiet surface.

But the lake was tiny, with an area of only 0.6 square miles. And with no other body of water connected to it, what could a vessel of that size be doing there?

Still, the stories about the gigantic ship persisted. They couldn’t have known then, but at the bottom of this tiny lake were two of the most unique artifacts ever to be uncovered from the ancient world.

Their story would span millennia, bridging the eccentricities of Rome’s most notorious Emperor and one of the twentieth century’s most reviled rulers — only to be lost forever in the fires of war.

Looking at the placid waters of Lake Nemi in the 15th century, none of that would have seemed plausible. But for years now, fishermen had been using grappling hooks to bring up ancient artifacts from the legendary wreck that lay beneath, and selling them in the markets.

An investigation was warranted. In 1446, a young Cardinal and nephew of the Pope named Prospero Colonna, decided to probe for himself the rumours of an unlikely shipwreck at the bottom of Lake Nemi.

He sailed out onto the lake, and sure enough, he could just make out a sprawling lattice of wooden beams. He and his men tried to send down ropes with hooks on the end to retrieve parts of this mysterious structure, but at a depth of 60 feet they didn’t have much luck.

All they managed was to tear off some planks. Colonna had confirmed that the wreck existed, but from there the mystery only deepened.